In a solar thermal power station, a certain number of heliostats are used to reflect the sunlight in an area into a heat absorber area, and the energy required for power generation is obtained by concentrating the sunlight. However, the position of the sun changes continuously with time, so the heliostats need to move continuously to correct the exit direction of the reflected light, so that the light spot can accurately fall in the area of the heat absorber, thus improving the working efficiency of the whole solar thermal power station.
The positions of celestial bodies (such as the sun, the moon, first-class stars, etc.) that move regularly and have a certain brightness can be accurately calculated by the corresponding astronomical formulas, that is, the incident vector at any given moment is known. The space positions of the heat absorber area and the heliostat are relatively fixed, i.e. the reflection vector at any moment is known. Therefore, in theory, for the heliostat with a fixed installation position, its mirror surface normal vector at any given moment can be accurately calculated, which is then decomposed into the rotation angle of the corresponding rotation axis according to the rotation mode of the heliostat, so as to realize the accurate mechanical motion of the heliostat.
Although sufficient mechanical motion accuracy of the heliostat has been ensured in design, various new errors will be introduced in the process of processing, manufacturing, transportation and installation as well as daily operation, such as tilt of the rotation axis of the heliostat, foundation deformation, installation attitude deviation, deformation of the supporting structure, etc., making the newly installed heliostat unable to meet the design requirements and its reflected spot position will shift, thus directly affecting the power generation efficiency. Therefore, after installation, the heliostat needs to be corrected to ensure the accuracy of its mechanical motion before it can meet the requirements of normal operation, which is also a routine workflow of the solar thermal power station.
At present, the heliostat correction technology mainly involves identification and processing of the reflected light spot. Chinese Patent (CN102937814B) first irradiates the light spot on a carrier, then calculates the precision of the heliostat by means of image acquisition and processing, and finally corrects the heliostat according to the result. Chinese Patent (CN103345261B) sets up a photosensitive array directly under the heat collector in the same direction, calculates the deviation of the light spot center according to the intensity of the output signal, and finally corrects the rotation corner of the heliostat. Chinese Patent (CN103728983A) installs an image acquisition device on the top of the tower to photograph a specific heliostat, and calculates the deviation between the actual rotation angle and the theoretical rotation angle from the light spot position obtained by acquisition. Although the above three methods are all traditional methods of heliostat correction, the number of heliostats that can be corrected at the same time is limited because the light spot carriers (white boards, photosensitive arrays, image acquisition devices, etc.) they use are installed on the tower.
In modern solar thermal power stations, there are usually thousands of heliostats, and the data points for heliostat correction need to cover the range of mechanical motion as much as possible in order to obtain the best correction effect. Obviously, the traditional correction methods with low efficiency usually take a long time to make the heliostats in the whole solar thermal power station reach the optimal working state, which can no longer meet the operational requirements of modern solar thermal power stations. Therefore, there is a need for a high-efficiency, high-precision and convenient method to correct heliostats, which can accurately correct any number of heliostats at the same time.